This invention relates generally to the weather disturbance analysis features of a weather radar display. More particularly, this invention relates to a weather radar display mode implementation which displays horizontal and vertical scans in an axonometric format for weather disturbance analysis purposes. Still more particularly, this invention relates to a weather radar system display mode implementation which enhances the ability of a user to simultaneously correlate the horizontal and vertical components of a weather disturbance to facilitate analysis of the disturbance.
Users of weather radar systems have different requirements, depending upon the particular application of the system. For example, users of weather radar systems for marine or small aircraft applications are typically interested in detection and avoidance of threatening weather disturbances. Users of such systems for land based and medium to large aircraft applications are interested in both detection and analysis of weather disturbances.
The intent of weather disturbance analysis is to issue warnings in the case of land based applications, and to make decisions to fly through or around the disturbance in the case of airborne applications. To assess the threat of a weather disturbance, both reflectivity, which relates to rainfall rate, and storm height need to be analyzed. The user needs substantial training and experience to be able to make an accurate analysis. In the case of airborne radar systems, pilot workload is a very important consideration in the design of the system. Pilots of high performance aircraft are often faced with selecting the least hazardous route and flying that route. This issue is magnified in a situation where a weather disturbance is combined with the need to approach and land at an airport. In these situations the weather radar system is a tool to facilitate analysis of the disturbance.
Conventional weather radar systems provide the user with either a plan position view or a vertical profile view on the radar system display.
The plan position view is a view looking down, with the radar system antenna scanning horizontally at a particular elevation angle. The coordinates are range and bearing. The elevation angle is generally available as a manual control to the user.
The vertical profile view shows a vertical slice at a particular bearing as viewed from the side. The coordinates are range and height.
A significant problem exists in correlating the plan position and vertical profile views to analyze weather disturbances.
The disadvantages of conventional weather radar system displays for the aforenoted purpose include: (1) a single horizontal or vertical view is the only view available at any given time; (2) it takes user skill to correlate the two views; and (3) continual switching between views as is necessary adds to user workload.
U.S. Pat. No. 4,940,987 (U.S. Class 342/26) which issued to Frederick on Jul. 10, 1990 provides for two simultaneous views of the weather disturbance, i.e. a plan view and a vertical side or frontal view. The net effect of this approach is to view a weather disturbance with two intersecting planes. One plane is the horizontal plan view, while the other plane is user selectable to be a vertical slice along the range axis, or a vertical slice perpendicular to the range axis. The vertical slices can be adjusted for their thickness so that, for example, a frontal view represents an integration of the data from a range "a" to a range "b". The disadvantages of this approach are: (1) the user must mentally correlate the two views; (2) the frontal view has a very long update rate; and (3) the radar system must have substantial hardware (memory) to support this approach.
U.S. Pat. No. 5,198,819 (U.S. Class 342/26) which issued to Susnjara on Mar. 30, 1993 teaches storing multiple plan views in their own display memories. The views are then displayed in an overlapping fashion, with only the highest of the stored views shown in true rainfall intensities. The concept of storage of multiple plan views suffers from a long lag time to fill all memory planes. Each horizontal scan usually takes several seconds to complete. Even if the currently scanned view is continuously updated, the displayed complete view has data that can be almost a minute old. This problem is especially evident when the vehicle carrying the radar system (such as an aircraft) changes heading. The overlapped views can be dangerous in that low altitude features of a weather disturbance can be overlooked. Also this concept is costly in that a memory plane is needed for all plan views. Finally, the display unit is complex and not readily available in current weather radar systems.
U.S. Pat. No. 3,044,058 (no class indicated) which issued to Harris on Jul. 10, 1962 implements an isometric display on a cathode ray tube (CRT). The purpose of the Harris invention is to show the spatial relationship of various targets relative to the user. The antenna in the Harris arrangement scans a volume, not two intersecting planes, with location of the target (aircraft, ship, etc.) being of prime importance, rather than the analysis of the internal content of a weather disturbance. The use of a CRT is an integral part of the Harris invention, whereas the intent of the present invention is to use a generic display device. Accordingly, Harris is seen to significantly differ from the present invention.